The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hydrocarbons (oil, condensate, and gas) are typically produced from wells that are drilled into the formations containing them. The oil or gas residing in a subterranean formation can be recovered by drilling a well into the formation. A wellbore is typically drilled down to the subterranean formation while circulating a drilling fluid through the wellbore. After the drilling is terminated, a string of pipe, e.g., casing, is run into the wellbore. Then, the subterranean formation is usually isolated from other formations using a technique known as well cementing. In particular, Also, for a variety of reasons, such as inherently low permeability of the reservoirs or damage to the formation caused by drilling and completion of the well, the flow of hydrocarbons into the well is undesirably low. In this case, the well is “stimulated” for example using hydraulic fracturing, chemical (usually acid) stimulation, or a combination of the two (called acid fracturing or fracture acidizing).
The drilling fluid, cementing fluid or stimulation fluid generally includes a fluid loss control additive to reduce the loss of fluid, e.g., water, from the fluid when in contact with permeable subterranean formations and zones. Fluid loss control plays an important role in those oilfield treatment fluids (fracturing, cementing, gravel/frac packing etc). Most of the treatments use a polymer based fluid (guar, guar derivative or hydroxy ethyl cellulose, etc.) to control leak off. These fluids build a low permeability filter cake that reduces the leak-off rate by reducing the diffusion rate of the solvent across the boundary between the bulk of the fluid and the formation (filter cake). For further decrease in leak-off rate macroscopic solids such as fine silica, calcium carbonate, mica, or clays are added to the fluid. Also, the addition of a second soluble polymer such as polyacrylamide, starch, xanthan, etc to the polymer based fluid is not uncommon to control fluid leak-off. One of the problems associated with the use of additives (solids/polymer) to control leak-off is their cleanup after the treatment is done. Inadequate cleanup can result in a decrease in oil/gas productivity. In addition, the use of second polymer gives rise to mixing issues at the surface and higher friction pressures due to increase in polymer loading
Consequently, there is a need for a fluid loss control additive that is more efficient. A method to control fluid leak-off is disclosed herewith using a hydrophobic polymer as a fluid loss additive for polymer based fluids. In addition to fluid loss control, the method also decreases the risk associated with cleanup and mixing on surface of the well bore.